Comparison of upgrades needs to recognize the difference in curve speeds

The example on the last page has compared a French standard train with a tilting train in the USA. A possible conclusion
could be, that not every tilting train uses its technical potential.

But the achieved curve speed values are quite close at least. This changes, if a standard Amtrak train and a European tilting
train are added:

curve radius

superelevation

speed limit 1

Amtrak, non-tilting

1000 feet

4 inches

42 mph

Amtrak Cascades, tilting

1000 feet

4 inches

48 mph

TGV, non-tilting

1000 feet

4 inches

53 mph

DB type 610 and similar

1000 feet

4 inches

63 mph

1 Other increments than 1 mph are ignored for speed restrictions. The reason is
explained here.

The allowed
unbalanced superelevation for standard
passenger trains is 3 inches in the USA, while some tilting trains in Spain, Britain, Finland and Germany got allowance
for 11.8 inches. While WSDOTs Talgos help to speed up Amtrak quite obviously, the result falls short of the technical
possibilities.

3 inches of unbalanced superelevation is the US standard, but the FRA allows 4 inches by waiver in some cases.

The operational reality is even more extreme, because expecting the same superelevation is not realistic. On a freight route
in the USA, 3 inches will be exceeded quite seldom. On mixed-usage track in Europe, the legal limit might not be used
normally, but 5 inches of superelevation for the tightest curves is a realistic assumption.

The type 610 DMU operates with up to 11.8 inches of unbalanced superelevation, allowed by waiver of the
Eisenbahnbundesamt, a German authority similar to the FRA.

If the different infrastructure is taken into account, the possible speed difference for the same curve becomes truly
amazing:

curve radius

superelevation

speed limit 1

Amtrak, non-tilting

1000 feet

3 inches

39 mph

Amtrak, non-tilting

1000 feet

4 inches

42 mph

DB type 610 and similar

1000 feet

4 inches

63 mph

DB type 610 and similar

1000 feet

5 inches

65 mph

1 Other increments than 1 mph are ignored for speed restrictions. The reason is
explained here.

So a curve with this radius might restrict a train to either 39 mph or 65 mph in everyday operation. This might be
enough evidence to assume, that "the track is curvy" is no sufficient explanation for the low speed of Amtrak
trains. And it might discourage the direct comparison of possible upgrade results in Europe, Japan and the USA.
Instead, a more detailed approach is unavoidable.